As a step-up transformer for generating a high voltage for a cathode ray tube, there has hitherto been proposed one which includes a plurality of secondary windings, for example, eight secondary windings laminated in a plurality of layers, for example, eight layers with insulating films therebetween, divided on the basis of a predetermined number of turns, and opened at one-side ends thereof, as shown in FIG. 9.
Referring to FIG. 9, symbol 10 denotes a commercial power source of, for example, 100 V and 50 Hz. One end and the other end of the commercial power source 10 are connected respectively to one end and the other end of a rectifying circuit 11 having a diode bridge configuration, a positive output terminal of the rectifying circuit 11 is earthed through a smoothing capacitor 12, and a negative output terminal of the rectifying circuit 11 is earthed.
The positive output terminal of the rectifying circuit 11 is connected to a power source terminal of an oscillation drive circuit 14 through a resistor 13, and the positive output terminal is earthed through a switching circuit 15 consisting, for example, of a series circuit of MOS-FET switching devices Q1 and Q2. The switching circuit 15 is so driven that the switching devices Q1 and Q2 show alternative conduction at a predetermined frequency by the oscillation drive circuit 14.
Furthermore, the switching circuit 15 constitutes a half-bridge circuit, the positive output terminal of the rectifying circuit 11 is connected to the drain of the switching device Q1, and the source of the switching device Q2 is earthed. In addition, damper diodes D1 and D2 are connected in parallel to the switching devices Q1 and Q2, respectively.
A connection point between the source of the switching device Q1 and the drain of the switching device Q2 is earthed through a series circuit of a resonant capacitor 16, a coil 17, and a primary winding 18 of a step-up transformer T.
The primary winding 18 of the step-up transformer T is supplied with a current at a resonance oscillation frequency intrinsic of the series circuit.
Symbols 19a, 19b . . . 19h denote eight secondary windings which, as shown in FIG. 11, are laminated on a bobbin 107 with insulating films 105 therebetween, are divided on the basis of a predetermined number of turns, and are opened at one-side ends thereof. Rectifying diodes 20a, 20b . . . 20h are each connected, in a vertical row fashion, to a point between the other-side ends of each adjacent pair of the secondary windings, of the eight secondary windings 19a, 19b . . . 19h. 
Specifically, the diode 20a is connected to a point between the other-side ends of the secondary windings 19a and 19b, the diode 20b is connected to a point between the other-side ends of the secondary windings 19b and 19c, the diode 20c is connected to a point between the other-side ends of the secondary windings 19c and 19d, the diode 20d is connected to a point between the other-side ends of the secondary windings 19d and 19e, the diode 20e is connected to a point between the other-side ends of the secondary windings 19e and 19f, the diode 20f is connected to a point between the other-side ends of the secondary windings 19f and 19g, the diode 20g is connected to a point between the other-side ends of the secondary windings 19g and 19h, and the diode 20h is connected to a point between the other-side end of the secondary winding 19h and the earth.
An equivalent circuit of the secondary winding system constituted of the eight secondary windings 19a, 19b . . . 19h and the eight rectifying diodes 20a, 20b . . . 20h is as shown in FIG. 10. By subjecting the voltages obtained at the secondary windings 19a, 19b . . . 19h to full-wave double-voltage rectification to produce DC voltages and laying up the DC voltages, it is possible to obtain a high DC voltage, for example, 32.4 kV. In FIG. 10, capacitors 21a, 21b . . . 21h are inter-layer capacitances of the secondary windings 19a, 19b . . . 19h. 
In addition, the other-side end of the secondary winding 19a is connected to a high-voltage output terminal 23 through a diode 22, and a connection point between the diode 22 and the high-voltage output terminal 23 is earthed through a smoothing capacitor 24.
Besides, the high-voltage output terminal 23 is earthed through a series circuit of resistors 25 and 26, a detection voltage of a high voltage obtained at a connection point between the resistors 25 and 26 is supplied to a control circuit 27, and the oscillation frequency of the oscillation drive circuit 14 is controlled according to a DC voltage obtained at the high-voltage output terminal 23 by the control circuit 27 so that the high DC voltage obtained at the high-voltage output terminal 23 will be constant.
Meanwhile, a sectional view of an example of the entire constitution of the high voltage generating transformer as shown in FIG. 9 is as shown in FIG. 12, in which symbol 101 denotes the secondary winding system. As shown in FIGS. 11 and 13, the secondary winding system 101 has a structure in which the eight secondary windings 19a, 19b . . . 19h in the state of being laminated in eight layers with the insulating films 105 therebetween are wound around the outer circumferential surface of the roughly cylindrical bobbin 107 having walls along both side edges, the insulating films 105 are, for example, belt-like in shape, and the secondary windings 19a, 19b . . . 19h are so wound as to have a width slightly smaller than the width of the insulating films 105.
Conventionally, the one-side ends and the other-side ends of the eight secondary windings 19a, 19b . . . 19h have been fixed by binding them respectively onto terminals 103 and 104 provided, through terminal bases 103a and 104a, on one side and the other side of the bobbin 107, and the diodes 20 and the like have been connected to the terminals 103 and 104 to assemble a circuit as shown in FIG. 9.
In addition, as shown in FIG. 12, the secondary winding system 101 is disposed so as to penetrate through a core 142, which forms a closed magnetic circuit at the center thereof, together with the bobbin 102a and a primary winding system 102 constituted of the primary winding 18.
However, when the one-side ends and the other-side ends of the plurality of windings, for example, the eight windings 19a, 19b . . . 19h are fixed by binding them respectively onto the terminals 103 and 104 as in the related art, where the number of the secondary windings 19a, 19b . . . 19h connected as required is eight, for example, the numbers of the terminals 103 and 104 provided on the bobbin 107 are each eight, i.e., a total of 16 terminals are needed, as shown in FIG. 13. Thus, in the related art, the number of the terminals needed is large, and the bobbin 107 is enlarged in size accordingly.
In consideration of the foregoing, it is an object of the present invention to make it possible to reduce the number of terminals required on a bobbin and to reduce the bobbin in size.